The invention relates to apparatus used in the lost foam casting process, and more particularly to batch hoppers used in the lost foam casting process.
As shown in FIG. 1, a conventional lost foam casting apparatus 1 includes a mold flask 3 adapted to contain a foam pattern (not shown), and a batch hopper 4 located above the mold flask 3 and adapted to dispense sand 5 into the mold flask 3. The batch hopper 4 includes a bottom wall 6 having therein a plurality of openings 7, and a sliding door or gate 9 that simultaneously opens and closes the openings 7. Such a gate 9 is shown in U.S. Pat. No. 4,593,739, which is assigned to the assignee hereof.
A disadvantage of this construction is that more sand falls through the openings 7 in the center of the hopper 4 than through the openings 7 near the periphery of the hopper 4 due to friction along the walls of the hopper 4 and due to the tendency of aggregate material to assume an angle of repose on its surface, both of which cause sand to slide toward the center of the hopper 4. Uneven flow rates of sand into the mold flask 3 can damage the foam pattern in the mold flask.
Attention is directed to the following U.S. patents:
______________________________________ Holmes 997,554 July 11, 1911 Rust 1,119,727 Dec. 1, 1914 MacDonald 1,127,471 Feb. 9, 1915 Tscherning 1,155,019 Sept. 28, 1915 Boynton 1,709,604 Apr. 16, 1929 Hutchinson 2,931,080 Apr. 5, 1960 Winter 2,859,497 Nov. 11, 1958 VanRens 4,593,739 June 10, 1986 ______________________________________
Attention is also directed to U.S.S.R. Pat. No. 770-646, and 1,266,642.